KR101944584B1 - Isolating water transport plates from elastomer seals - Google Patents

Abstract

The fuel cell stack 11 includes a plurality of adjacent fuel cells 13 and each fuel cell includes a single electrode assembly 15 (see FIG. 1) interposed between the anode anode water supply plate 22 and the cathode water supply plate 18 ). In the region where the silicone rubber 29 or other elastomer covers the fuel cell, adjacent edges of the water delivery plate are replaced by an elastomer-impermeable material 34 to form a seal with the external manifold 27 Or reinforced with an elastomer-impermeable material 34. This prevents the injection of the elastomer to the WTP, which can cause sufficient hydrophobicity to reduce or eliminate the water bubble pressure required to isolate the reactant gas from the coolant water, thereby preventing gas inhibition of the coolant pump . The preformed insert 34 may be cast into the transfer plate as it is molded or it may be cast in a fluid form of a meltable or hardenable non-elastomeric polymer, the elastomer- And subsequently melted or cured.

Description

[0001] ISOLATING WATER TRANSPORT PLATES FROM ELASTOMER SEALS [0002]

The Government has the right to the invention and all patents granted to it by the Contract No. FTA MA-04-7002 on the FTA National Fuel Cell Bus Program-Nutmeg Program .

A porous hydrophilic fuel cell substrate having a water channel on one surface and a reactant gas channel on an opposing surface, typically referred to as a water distribution plate (WTP), has a WTP Within the corners of the WTP, which can be hydrophobic, it has an elastomeric impermeable material, thereby eliminating water and bubble pressure, which prevents the gas from crossover into the coolant.

Referring to Figure 1, in a unified electrode assembly 15, a known stack 11 of fuel cells 13 that applies a gaseous reactant to a proton exchange diaphragm electrolyte employs a porous hydrophilic separator plate , And such a separator typically has a groove 16 for water, typically for water, for the coolant on the gas reactant grooves and the opposing surface on one surface of each substrate. The cathode water delivery plate 18 of one fuel cell flows the oxidant in the reactant gas grooves 19 and the anode water distribution plate 22 of the adjacent fuel cell in contact therewith contacts the reactant gas grooves 23 ). ≪ / RTI > The fuel and the oxidant are separated from each other by water in the pores of the water distribution plate, and the capillary force of such pores requires that the bubble has a certain pressure in order to pass water, and such pressure is called bubble pressure.

As the fuel cell stack is assembled, the dimensional tolerances and placement tolerances of the water delivery plates to each other and to the unified electrode assembly are greater than the dimensional tolerances of the WTP 18, 22 and the unified electrode assembly 15 at different heights Resulting in substrate edge misalignment, referred to as "skyline ". Thereby, an elastomeric filler, such as silicone rubber 29, is used to provide a relatively smooth area for sealing the fuel cell edge against the surface of the external reactant gas manifold, such as oxidizer manifold 27, Is applied to the uneven edge surface of the fuel cell. This allows a sufficiently smooth bed for the rubber gasket 30 to pass between the edge of the manifold 27 and the silicon 29, as described in U.S. Patent Nos. 6,660,422 and 7,122,384, both of which are incorporated herein by reference. to provide. In some cases, a thin rigid strip, which may be a dielectric, is provided between the rubber gasket and the silicon 29.

In regions where the manifold 27 is sealed to the fuel cell 13, the leakage of reactive gases from the channels 19, 23 to the coolant in the channels 16 occurs to such an extent that the coolant pump fails to function . This occurs in all fuel cell stacks and limits the lifetime of the stack. It has also been found that replacement of the outer portion of the seal, such as a fresh layer of silicone and / or a new rubber gasket 30, is not effective in most cases. Typically, the laminate must be reassembled. After decomposition, the affected cell becomes useless and, at best, the material is recycled.

Referring now to FIG. 2, it has now been discovered that the leakage between the reactant gas channel and the water channel is caused by a loss of bubble pressure within the WTP.

This again infuses the elastomeric polymer, such as silicon, into the porous structure of the feed plate 18, 22 from the seal at the edge of the fuel cell component, as shown by arrow 32, In the case of the control group.

The elastomer is very hydrophobic and coats the existing surface of the pores without filling the pores, so that the area where the silicone has penetrated becomes hydrophobic. When the degree of injection is sufficient, a reactant gas (typically, high pressure) is delivered into the water channel 16 (typically, low pressure). The coolant system eventually entrains the gas to a sufficient degree to cause the coolant pump to no longer effectively propel the coolant liquid and thus cause the system to stop.

Embodiments herein provide an elastomer-impermeable material that, at each edge of the WTP near the elastomeric sealing member, blocks the elastomer from being injected into the WTP. This embodiment prevents the elastomer from hydrophobizing the edge of WTP, eliminating the loss of bubble pressure and preventing the injection of gas into the coolant system. The material extends about 1 cm (1/3 inch) over the entire thickness of the WTP past the elastomer and within a short distance within the WTP.

The material may be pre-cast and molded into the WTP when the WTP is formed. Alternatively, the material may be deposited in a fluent form in the pores of the unmasked portion of the WTP, and then solidified by fusing or curing under WTP molding temperature.

Other variants will become more apparent in light of the following detailed description of exemplary embodiments, which has been described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a fragmentary perspective view of a fuel cell component, shown at an exaggerated ratio, below the edge of an external manifold with a rubber gasket and a silicone seal.
Figure 2 is a fragmentary perspective view of Figure 1 showing the injection of silicon into the WTP.
Figure 3 is a fragmentary perspective view of Figure 1, including a silicone-impermeable insert according to this aspect.
4 is a fragmentary perspective view of the edges of the mold registered in the silicon-impermeable insert prior to molding of the WTP, shown in exaggerated proportions.
5-7 are fragmentary perspective views of an alternative embodiment of the silicone-impermeable insert of this embodiment.

Referring to Figure 3, a first general embodiment of the present embodiment is shown in Figure 3, with the elastomer-impermeable insert 34 preformed at the edge of each WTP in the region of the silicon 29 into the water delivery plate WTP It prevents silicone or other elastomer from being injected. As used herein, the phrases "within" and "within proximity" include those intended for future use. The insert 34 prevents silicone from being injected into the water delivery plate and prevents any breakdown of the bubble pressure of the water delivery plate.

The insert 34 may be provided by placing the insert 34 into the edge of the mold 36 prior to filling the mold with a graphite / resin (or other suitable mixture) (FIG. 4). In Fig. 4, only the mold side and bottom adjacent faces 38-40 are shown. A pin 43 is affixed to the lower surface 38 of the mold in order to fill the mold with a conventional graphite / resin mixture and to assist in ensuring proper alignment in the mold during the process of molding the WTP, But only guides partially through holes 44.

In order to assist in coupling the insert 34 to the WTP during the molding process, some surface enlargement is provided to assist in the engagement of the insert 34 to the WTP. In the embodiment of FIG. 4, there are slots 46, 47 in each of the two individual edges 50, 51 of the insert 34 to be adjacent to the WTP.

Figure 5 illustrates that a wavy surface 53 may be used in place of the slots 46 and 47 to increase the adhesion between the insert 34 and the WTP 18,22. The vibrating surface 53 may be gently waveed, sharpened, or may be more like a saw blade. However, it is advantageous to provide a surface that is generally perpendicular to the edge of the WTP where adhesion is desired.

Figure 6 illustrates that the use of holes 55 can increase the surface area and improve adhesion between the insert 34 and the WTP 18,22.

FIG. 7 illustrates that the rib 56 can be used to increase the surface area and improve adhesion between the insert 34 and the WTP 18,22.

Another provision for indexing the insert 34 with respect to the mold 36 may be used in place of the holes and pins 43,44. However, it is not necessary that the passages through any indexing means in which the elastomer / silicone is selected necessarily be accomplished.

In a second general embodiment of the invention, instead of casting the pre-form into a molded WTP, the WTP would be able to be completed in a conventional manner, followed by the use of an elastomer-impermeable material Masked on one surface. The elastomer-impermeable material of the flexible form of a fusible or curable, non-elastomeric polymer is then deposited into the pores of the full thickness of WTP in the vicinity of the elastomeric seal and subsequently melted or cured.

The fluid material may be a suitable fine powder of a non-elastomeric, elastomeric, impermeable, meltable plastic or eutectic mixture selected from bismuth, lead, tin and cadmium.

There is no intention to limit the disclosure to the extent required by the appended claims, since changes and modifications of the disclosed embodiments may be made without departing from the spirit of the concept.

Claims (16)

An electrode assembly (15) comprising a plurality of mutually adjacent fuel cells (13), each fuel cell comprising a cathode catalyst and a proton exchange membrane interposed between the catalyst support and an anode catalyst and a catalyst support, A porous hydrophilic anode water delivery plate (18) disposed, a porous hydrophilic cathode water delivery plate (22) arranged adjacent to the cathode catalyst support;
A fuel cell stack (11) comprising an elastomeric seal (29) covering an edge of the fuel cell in an area where an external manifold (27) is sealed to the fuel cell, wherein:
A fuel cell stack (11) characterized by an insert (34) comprising an elastomer-impermeable material disposed within the entire thickness of each water delivery plate at a proximal portion of the elastomeric seal. The method according to claim 1,
Characterized in that said insert (34) is prefabricated with an elastomer-impermeable material and cast into an associated water delivery plate when said water delivery plate is molded. 3. The method of claim 2,
The fuel cell stack (11) according to any one of the preceding claims, further comprising an edge of each of the inserts (34) in contact with the water distributing plate (20) comprises a contact force-increasing surface enlarging portion (46, 47; 53; 55; 56). The method of claim 3,
Wherein the adhesion-increasing surface-widening portion comprises slots (46, 47). The method of claim 3,
Further comprising the at least one hole (55). ≪ RTI ID = 0.0 > 11. < / RTI > The method of claim 3,
Wherein the adhesion-increasing surface enlargement comprises a wavy surface (53). The method of claim 3,
Further comprising a rib (56). ≪ RTI ID = 0.0 > 11. < / RTI > The method according to claim 1,
The fuel cell stack (11) further characterized in that the elastomer-impermeable material comprises non-elastomeric plastic. The method according to claim 1,
The fuel cell stack (11) further characterized in that the elastomer-impermeable material comprises a metal. The method according to claim 1,
Wherein the elastomer-impermeable material is deposited in a fluid form in the pores of the total thickness of each of the water delivery plates in the vicinity of the elastomeric seal and then melted or cured in situ, A fuel cell stack (11) further characterized by comprising a porous, non-elastomeric polymer. 11. The method of claim 10,
The fuel cell stack (11) further characterized in that the elastomer-impermeable material comprises non-elastomeric plastic. 11. The method of claim 10,
The fuel cell stack (11) further characterized in that the elastomer-impermeable material comprises a metal. 13. The method of claim 12,
Wherein the elastomer-impermeable material comprises a process mixture selected from bismuth, lead, tin and cadmium. The porous, hydrophilic water delivery plates 18, 22 in the fuel cell stack 11 are formed by providing the elastomer-impermeable material within the entire thickness of each water delivery plate in the vicinity of any elastomer seal. To prevent the elastomeric sealant (29) from being injected therethrough. 15. The method of claim 14,
Wherein said providing step comprises casting a preformed insert (34) of the material into each of the water delivery plates (18, 22) when the water delivery plate is molded. 15. The method of claim 14,
The method of claim 1, wherein the providing step comprises applying a meltable or curable, non-porous, non-elastomeric, elastomer-impermeable material to each of the water delivery plates (18, 22) in the proximity of the elastomeric seal (29) In a fluid form in the pores of the total thickness of the first and second layers, and then melting or curing the material.

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